Two forms are admissible in the vocative case; facility of pronunciation is the best guide, e.g. Gaḃ i leiṫ, a Ḃrianaiġ. Come here, O’Brien. A Ṁic Uí Laoġaire, O’Leary. A Ṁic Uí Ṡuiḃne, MacSweeney.
487. Surnames occurring in Ireland to-day are of three classes: (1) Surnames of Gaelic origin. These in almost every instance have the prefix Ó (Ua) or Mac for a male, and Ní or Nic for a female. (2) Surnames of old foreign origin. The majority of these have no prefix. (3) Surnames of late foreign origin. Only a few of these have acquired a distinct form, pronounced in an Irish way.
488. When the surname is preceded by any ot the words Ó, Mac, Ní, Nic, the surname is in the genitive case, and is aspirated after Ní or Nic, but not after Ó or Mac: e.g., Seaġán Mac Doṁnaill, John McDonnell; Máire Ní Ċonaill, Mary O’Connell; Diarmuid Ó Conaill, Dermot O’Connell; Nóra Nic Ḋoṁnaill, Nora McDonnell.
489. When the whole name is in the genitive case, the words after Uí (gen. of Ó or Ua) and Ṁic (gen. of Mac) are aspirated; Ní and Nic do not change in genitive. Leaḃar Ṡeumais Uí Ḃriain, James O’Brien’s book; bó Ḃriain Ṁic Ḋoṁnaill, Brian McDonnell’s cow.
490. Mac and Ó aspirate when they really mean “son” and “grandson” respectively.
